1. Field of the Invention
The present invention relates generally to image processing apparatuses, and more particularly to an image processing apparatus capable of processing a large-sized document.
2. Description of the Related Art
An apparatus has been proposed which divides a large-sized document too large to be wholly placed on a platen into a plurality of images having overlapping portions with each other (a plurality of images having a size placeable on the platen), sequentially reads the images to store in the memory, and combines the divided images for output.
U.S. Pat. No. 5,465,163 discloses an apparatus and a method for reading a plurality of images having overlapping portions with each other divided from a large-sized original image, recognizing the overlapping portions of the divided images through pattern matching to locate border lines with not-overlapping portions, and combining the divided images along the border lines.
As one such conventional technique related to combination of images, U.S. Pat. No. 4,692,812 discloses an apparatus making such a control that a plurality of images having overlapping portions with each other divided from one original image are read, and two adjacent divided images are joined at their overlapping portions and combined, at which time the overlapping portions of the two divided images are each divided into strip shaped small regions, and the strip shaped small regions are alternately selected from the divided images and arranged.
Japanese Patent Laying-Open No. 3-182976 discloses a method of joining two images taken to have overlapping portions. According to the method the densities of the images are converted to be equal and binarized, two feature particles are extracted from each of the binarized images, and the images are joined along a joining line, i.e., a straight line connecting the barycenters of these feature particles. The feature particles herein are produced by extracting particulate small regions formed of a particular number of pixels and determining the particular number of pixels such that the number of small reasons is 2.
The above documents each disclose a joining technique which avoids loss and overlap of images. More specifically, by each of the above joining methods, the adjacent portions of images are read in an overlapped manner so that no part of the original image is lost at the joining part, and border lines (joining lines) are produced within the overlapped regions or at ends and the overlaps are joined and overlaid along the border lines so that overlap or offset of the images do not occur at the joining part.
Corresponding portions between the read images within overlap regions sometimes have different densities. Therefore, such method of joining images while simply avoiding loss and offset of images or overlap of images is encountered with a disadvantage that a line-shaped joining part is recognized because of the density difference.
According to each of such conventional techniques, two partial images are joined by determining a joining position based on the same method regardless of kinds of documents. Therefore, relatively complicated and inaccurate methods are applied in the case of newspaper in which the joining positions may be determined more accurately or more simply taking advantage of the distinctive frames or rules.
The method of determining the position of arranging the partial images through pattern matching of overlaps as disclosed in U.S. Pat. No. 5,465,163 requires a long period of time for its complicated processing and frequently causes erroneous determination.
According to the method disclosed in Japanese Patent Laying-Open No. 4-331567, the direction of placing an original must be predetermined in order to read partial images, which imposes the operator much labor for its complicated operation at the time of setting the original. If the original is set in a wrong direction, an image combination error occurs. For some apparatuses, it may difficult to set partial images in a determined direction.